1. Field of the Invention
The present invention relates to a light source holding structure, a light source holding member, a light source unit, and a display device. More specifically, the present invention relates to a light source holding structure to be incorporated in a light source unit for a display device such as a liquid crystal display device, a light source holding member which can be used in the light source holding structure, a light source unit using the light source holding structure, and a display device.
2. Description of the Related Art
A display device having a non-self-emissive display panel such as a translucent liquid crystal display panel generally has a configuration such that a light source unit in which a light source is incorporated is provided on a back side or a lateral side of the display panel. For the light source which is incorporated in the light source unit, a substantially linear or substantially U-shaped fluorescent tube is widely used. A light source clip is used for fixing the light source to a chassis of the light source unit (see Japanese Patent Application Unexamined Publication No. 2004-348150).
FIG. 19 is an exploded perspective view schematically showing a conventional example of the configuration of the relevant portion of a light source unit for a display device in which a plurality of light sources are incorporated. A light source unit 9 for a display device in FIG. 19 has a chassis 91, a plurality of linear light sources 93, a plurality of light source clips 92 for fixing the light sources 93 to the chassis 91, and other given constituent elements.
Each of the light source clips 92 has light source holding portions capable of holding tube bodies of the light sources 93 and a locking portion for attaching the clip 92 to the chassis 91. A plurality of through holes (not shown) are provided in given positions on a bottom plate of the chassis 91. The locking portions of the light source clips 92 are caught in the through holes, by which the light source clips 92 can be attached to the chassis 91. In addition, the tube bodies of the light sources 93 are held at one or some positions by the light source holding portions of the light source clips 92, by which the light sources 93 can be fixed to the chassis 91.
However, the following problems could arise when the light sources 93 are fixed to the chassis 91 by holding the tube bodies of the light sources 93 at one or some positions by the light source clips 92 as described above.
It is a known characteristic of fluorescent tubes used as the light sources that when temperature distribution of tube bodies of the fluorescent tubes becomes non-uniform during the use of the fluorescent tubes, the amount of light emitted by the fluorescent tubes also becomes non-uniform depending on the temperature distribution. To be specific, the amount of light emitted becomes larger in high temperature portions of the tube bodies and becomes smaller in low temperature portions of the tube bodies.
When the material of the light source clips 92 has higher thermal conductivity than air, heat of the light sources 93 is easily transferred to the chassis 91 through the light source clips 92. Thus, the temperatures of the light sources 93 are locally lowered in the portions at which the light sources 93 are held by the light source clips 92 and in the vicinities of the portions as compared to the other portion. As a result, the amount of light emitted is locally lowered in the portions at which the light sources 93 are held by the light source clips 92 and in the vicinities of the portions as compared to the other portion.
If the light sources 93 have portions at which the amount of light emitted is locally lowered, lower luminance portions could appear locally on a display screen (i.e., luminance irregularity could occur) when the light source unit 9 is incorporated in and used in the display device. Because such luminance irregularity decreases display quality of the display device, it is preferably prevented or minimized.
There is proposed a configuration in which the light source clips are arranged in a zigzag pattern on the chassis in order that luminance irregularity may be made less noticeable (see Japanese Patent Application Unexamined Publications Nos. 2004-348150 and 2004-318176). This configuration prevents portions at which the luminance is locally lowered due to radiation of heat through the light source clips from being aligned linearly in a specific direction. Thus, luminance irregularity can be made less noticeable even if the light sources have portions at which the luminance is locally lowered.
However, the above configuration is effective for making low luminance portions less noticeable but not for preventing the light sources from having portions at which the amount of light emitted is locally lowered. In accordance with a recent increase in the size of the display panel, the length of the fluorescent tubes to be used as the light sources becomes longer. Accordingly, in order not to break the light sources to be incorporated in the light source unit, it is necessary to increase the number of positions at which the tube bodies of the light sources are held by the light source clips. By doing so, the number of lower luminance portions on the display screen is increased, and the lower luminance portions could become easily noticeable.